The Low Speed Intermittent Region of a Single Stream Shear Layer (SSSL)

External intermittency: intermittent presence of vortical fluid, exists on the high and the low speed sides of a SSSL. From Corrsin and Kistler (1954) it is understood that the vortical fluid is bounded by a viscous superlayer (VSL) that is well-defined given zero vorticity in the entrained fluid. That condition is met for the SSSL flow of Morris and Foss (2003). The smoke trace from an incense stick provides a convenient technique to mark the 3-D locations of the VSL. Specifically, the vorticity at the VSL ``shreds'' the end of the trace; the shredding is captured by two cameras with calibrated x-y=f(z) and y-z=g(x) image planes. Complementary transverse vorticity measurements were acquired in the spatial domain indicated by the ``shredding.'' Interpreted results will be presented. Corrsin, S. and Kistler, A.L. (1954) ``The Free Stream Boundaries of Turbulent Flows,'' NACA TN 3133. Morris, S.C. and Foss, J.F. (2003) ``Turbulent boundary layer to single-stream shear layer: the transition region'', Jour. Fluid Mechanics, 494, pp. 187-221.